Functional correlates of auditory structures in the brainstem and periphery will be studied. The discharge characteristics of single-units in the lateral superior olive (LSO) of the decerebrate cat will be investigated. Two experimental paradigms will be followed. In the first, the nature of the ipsilateral inputs will be examined by functionally isolating the nucleus from its contralateral input. In the second, the neuronal response to dichotic transient sounds will be explored. These investigations will attack the general neurophysiological problems of excitatory-inhibitory interactions as well as the more specific functions the LSO serves in the analysis of binaural hearing. Particular attention will be given to its possible role in the detection of the short interaural-time differences involved in the localization of transients. A second study seeks to explore the functional differences between inner and outer hair cells of the guinea pig organ of Corti. Horseradish peroxidase (HRP) is introduced into the perilymph in order to determine difference in synaptic activity between the two types of hair cells and how it varies with acoustic stimulation. A small general purpose computer assists in stimulus control, data acquisition, data storage, and analysis in both the single-unit and HRP experiments. BIBLIOGRAPHIC REFERENCES: Brownell, W.E., Fleshman, J.W., Jr., Karlan, M.S., Inner and outer hair cells, differential uptake of horseradish peroxidase: A preliminary report, Trans. Am. Acad. Opthalmol. Otolaryngol., (1977) in press. Duffy, D.J., Brownell, W.E., File format for neurophysiology data collection, proceedings of DECUS, June, 1977, in press.